The invention relates to radiant heaters, and more particularly to an improved gas-fired infrared heat generator.
The type of tool to which this invention relates is disclosed in U.S. Pat. Nos. 3,040,805, 3,129,749, 3,198,240 and 3,814,573. Such a device generally burns a fuel such as propane from a pressurized source mixed with air in a combustion chamber which is defined by an inner mantle or gas diffuser and an outer grid across the face of the tool. The gas diffuser usually comprises a series of overload wire grids of various opening sizes which disperse the effluent gas streams so finely that the burning actually takes place on and adjacent to the surface of the wire grids. A red-hot glow is produced across the grids, and intense infrared radiation is emitted therefrom. Generally a reflector enshrouds the face of the gas diffuser to directionally intensify the radiant heat given off by the tool. The infrared heating tools are used for a variety of purposes including paint and wall paper removal and numerous heating, thawing and drying purposes.
Infrared heat generators generally include a manually operable rotatable screw-type valve for initiating and regulating the flow of gas into the combustion chamber. While this arrangement is very convenient, it can be extremely hazardous under certain circumstances. For example, if the operator either carelessly leaves the tool burning or suffers a disabling attack of some kind while he is operating the tool, the danger of starting a fire is very high. This is particularly true with a heavy duty type burner which is capable of applying a great deal of intense heat to closely positioned objects and structures.
Another difficulty and often potential hazard encountered with present infrared heat generators is that they generally have no provision establishing a minimum distance between the diffuser and the work surface, except for the limitation proposed by the reflector itself. Because such provision is lacking, severe scorches and fires on the work can easily be caused by an overzealous operator holding the tool too close to the work during, for example, paint stripping or wall paper removal. The sub-visual radiant nature of the heat produced often causes an operator to lose sight of the high intensity of the heat.
A less serious difficulty often encountered with many present radiant burners is the invasion of their fuel lines and fuel-air mixing chambers by insects. The air intake openings of the tool provide access for the insects, which typically nest inside the gas line and mixing chamber, clogging gas openings and reducing or nullifying the output of the tool. Spiders in particular cause a great deal of such trouble.